A wireless local area network (LAN) system faces in some cases propagation loss, shadowing, fading, collision between frames, or the like, and so a phenomenon may occur in which a receiver fails to receive a frame transmitted from a transmitter. In order to address such a phenomenon, the wireless LAN system may employ retransmission control using an acknowledgment (ACK) and a negative-acknowledgment (NACK) in some cases. In the retransmission control techniques using a response from the receiving side, the receiving side may return an acknowledgment response including information indicating success or failure of data reception in response to an acknowledgement request from the data transmitting side. An example of the techniques includes the retransmission control using a Block ACK Request (BAR) frame and a Block ACK (BA) frame, which allows acknowledgements for reception related to one or more transmission frames to be executed together.
Here, IEEE802.11aa, which is one of the standards for wireless LAN, defines the technique for performing the retransmission control using the BAR and the BA is performed between a parent device (Access Point: AP) and a slave device (Station: STA). Specifically, the technique is defined in which the AP transmits by unicast the BAR to a plurality of STAs belonging to a multicast group and receives the BA from the STA, thereby performing the retransmission control relating to multicast transmission. This technique makes it possible, in the case where the number of STAs belonging to a multicast group is small, to achieve a highly reliable wireless communication environment by allowing the AP to transmit the BAR to all the STAs and to receive the BA from all the STAs, in one example. However, in the case where the number of STAs belonging to a multicast group is large, the overhead of transmitting and receiving the BAR and the BA may deteriorate the throughput.
In view of the above circumstances, Patent Literature 1 below discloses a technique of grouping STAs of a multicast group and performing transmission and reception of the BAR and the BA to and from only a representative terminal set for each group.